This application is based on and claims priority to Japanese Patent Application No. 2000-145986, filed May 18, 2000, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
This invention generally relates to a shaft coupling for an outboard motor, and more particularly relates to an improved shaft coupling for an outboard motor that has a lubricant chamber around shafts of the coupling.
2. Description of Related Art
An outboard motor typically comprises a power head including an internal combustion engine and a housing unit that depends from the power head. Some outboard motors also have an intermediate member positioned between the power head and the housing unit to support the engine above the housing unit. The engine generally includes a vertically-extending crankshaft that passes through an aperture defined at a bottom end of the engine body. The housing unit that depends from the power head generally encloses a vertically-extending driveshaft, which drives a submerged marine propulsion device.
The crankshaft typically comprises a lower recessed portion that receives an upper portion of the driveshaft such that the two shafts can be coupled together. The shaft coupling typically is made as such that the recessed portion of the crankshaft comprises inner spline grooves and the upper portion of the driveshaft comprises outer spline grooves that engage with the inner spline grooves of the crankshaft. The driveshaft, thus, is rotatably coupled to the crankshaft and can be driven by the crankshaft through the shaft coupling when the engine operates. The intermediate member, because of this coupling configuration, also defines an aperture through which the driveshaft extends downward from the crankshaft.
Usually, grease lubricates the shaft coupling. In order to enclose the grease around the coupling, the engine body and the intermediate member are coupled together in a fluid-tight manner. In addition, to reduce the amount of grease leaking out through the aperture of the intermediate member, seal members generally are disposed between an inner surface of the recessed portion and an outer surface of crankshaft and between an inner surface of the aperture of the intermediate member and an outer surface of the driveshaft housing.
Even with such a sealing arrangement, the grease is lost over time. The loss of grease generally occurs because the sealing arrangement is not perfect and the grease slowly works its way out of the chamber created among the seals due to the rotational movement of the driveshaft and the crankshaft. As the grease escapes, the coupling begins to prematurely wear at or around the spline connection. The wear produces metal dust, flakes and shavings in the coupling region. The metal dust, flakes and shaving can gall the coupling such that the driveshaft and the crankshaft become difficult to separate during maintenance. Furthermore, water also can work into the chamber in which the coupling is positioned after some of the grease has escaped. The water can rust or corrode the shafts over time and can work to displace further grease.
One appropriate way to resolve this problem is to disassemble the coupling and to repack grease around the coupling. This method, however, is quite troublesome and time consuming. Under the circumstances, users of the outboard motors dislike disassembling the shaft coupling and the shaft coupling is likely to be improperly maintained. A need therefore exists for an improved outboard motor shaft coupling that can maintain its state of lubrication.
In accordance with one aspect of the present invention, an outboard motor comprises an internal combustion engine. The engine includes an engine body and an output shaft. The engine body defines a first aperture through which the output shaft extends and is journaled. The output shaft has a recessed portion. The recessed portion defines inner spline grooves. A support member supports the engine body. The support member defines a second aperture. A driveshaft extends through the second aperture toward the recessed portion. The driveshaft has a tip portion defining outer spline grooves. The outer spline grooves are coupled with the inner spline grooves so that the driveshaft is connected to the output shaft for rotation together with the output shaft. A first seal member is disposed between an outer surface of the output shaft and an inner surface of the first aperture. A second seal member is disposed between an outer surface of the driveshaft and an inner surface the second aperture. The engine body, the support member, the output shaft, the driveshaft and the first and second seal members together define a lubricant chamber to enclose lubricant.
In accordance with another aspect of the present invention, an outboard motor comprises an internal combustion engine. The engine includes an engine body and an output shaft. The engine body defines a first aperture through which the output shaft extends and is journaled. The output shaft has a recessed portion. The recessed portion defines inner spline grooves. An exhaust system is arranged to discharge exhaust gases from the engine. An exhaust guide member defines a portion of the exhaust system and supports the engine body. The exhaust guide member defines a second aperture. A driveshaft extends through the second aperture toward the recessed portion. The driveshaft has a tip portion defines outer spline grooves. The outer spline grooves are coupled with the inner spline grooves so that the driveshaft is connected to the output shaft for rotation together with the output shaft, and means are provided for trapping lubricant at least around the inner and outer spline grooves.
In accordance with a further aspect of the present invention, a shaft coupling is provided for an internal combustion engine. The shaft coupling comprises an engine body. An output shaft extends through an aperture defined in the engine body. A coupling member is adapted to couple the engine body to a housing of the driven shaft. The coupling member is fluid-tightly affixed to the engine body. A driven shaft extends through a through-hole defined in the coupling member to be coupled with the output shaft. A first seal is arranged to seal between the engine body and the output shaft. A second seal is arranged to seal between the coupling member and the driven shaft. The second seal has a base portion and a pair of seal portions bifurcated from the base portion. The seal portions abut on the outer surface of the driven shaft. The engine body, the output shaft, the coupling member, the driven shaft and the first and second seals together define a lubricant chamber.